Method of selecting automatic operation mode of working machine

ABSTRACT

Even when a bucket is changed to an optional special bucket, path control as intended by an operator can be automatically performed without making a correction of the angle of the original bucket. For this purpose, in an operation mode determining section (9), there is calculated the possibility (U2) of an operation mode being a nose-fixed mode, depending on how much a bucket attitude angle (γ) deviates from a predetermined angle, and there is also calculated the possibility (U1) of the operation mode being the fixed-angle to the ground mode, depending on the magnitude of a computed value of the allowable angle held with respect to the ground, whereby the operation mode during the automatic path control can be automatically determined by comparing these possibilities (U1, U2).

TECHNICAL FIELD

The present invention relates to construction equipment with a link-typeworking machine having a bucket or the like, such as a hydraulic powershovel, wherein path control of the tip of the working machine iscarried out, and to a method of selecting an automatic operation modefor the working machine whereby a determination, of whether the controlof an angle to the ground of the tip of the working machine should becarried out, is automatically made without requiring an input by anoperator.

BACKGROUND ART

FIG. 1 shows a working machine of a hydraulic power shovel comprising aboom 1, an arm 2, a bucket 3, a boom cylinder 4, an arm cylinder 5, anda bucket cylinder 6. The boom 1, the arm 2, and the bucket 3 are movedby extending or contracting the cylinders 4, 5, or 6, respectively,causing a distal end of the bucket 3 to follow a predetermined path forexcavation.

Conventionally, there are two modes of operation in automatic excavatingpath correction work by a hydraulic power shovel on a slope. In one mode(nose-fixed mode), as shown in FIG. 2A, the axes of the boom 1 and thearm 2 are activated in an interrelated manner to make the bucket noseexcavate and finish a flat surface. In the other mode (fixed-angle tothe ground mode), three axes, namely, the boom 1, the arm 2, and thebucket 3 are activated in an interrelated manner to perform excavationand surface finishing using a bottom surface of the bucket, as shown inFIG. 2B. Before beginning automatic operation, an operator must use aswitch or the like to select between these two modes.

A prior art system for automatically selecting between the modes isdisclosed in Japanese Patent Laid-Open No. 2-47432 publication, whereina boom angle θ₁, an arm angle θ₂, a bucket angle θ₃, a body inclinationθ₀, and a target excavating grade θ, shown in FIG. 3 are inputted. Anangle β between the bottom surface of the bucket 3 and the flat surface,which is to be excavated, is determined at the beginning of theautomatic operation from formula (1) below, and the computation resultis compared with a predetermined value, thereby automaticallydetermining the mode.

ti β=3/2π-(θ₀ +θ₁ +θ₂ +θ₃ +θ+α) (1)

(where e is the nose angle of the bucket).

Generally, in the case of the bucket used for the hydraulic powershovel, a standard tooth bucket shown in FIG. 4A needs to be replaced byvarious special buckets according to the particular work. On the otherhand, however, a slope finishing bucket, shown in FIG. 4B, comes in aninfinite number of shapes with more buckets being produced at generaliron works, than genuine buckets produced by construction equipmentmanufacturers. Buckets produced by general iron works vary in dimensionsfrom one bucket to another except for pin intervals of the buckets. Inother words, the use of a method, wherein the mode is determined bydetermining the angle to the ground β of the bucket bottom surface,poses a problem in that the nose angle α of the bucket must be correctedeach time the bucket is changed except when a bucket having apredetermined shape is used.

Further, a problem arises when automatic operation is performed forpurposes other than excavation. For example, if the position of a hookis linearly moved in suspension work, as shown in FIG. 5, the automaticdetermination by the described mode determination method erroneouslyselects the nose-fixed mode because of a significant difference betweenthe target direction of movement and the orientation of the angle βbetween the bottom surface of the bucket and the ground. This presents aproblem in that the nose point moves as indicated by a solid line ratherthan moving along the path intended by the operator and indicated by abroken line.

Hence, in order to maintain the current angle to the ground β when thedirection of the movement of the working machine is given, the bucket 3must be turned either to a dump truck side or an excavating side. Forinstance, as shown in FIG. 6A, if the angle of movement of the bucket 3on the excavating side is small, then it soon becomes impossible tomaintain the angle to the ground β in the fixed-angle to the groundmode. Therefore, it is very likely that the operator's intention is thenose-fixed mode. On the other hand, if a bucket attitude angle γ, whichis the attitude of the bucket 3 with respect to the arm 2, is large asshown in FIG. 6B, then the resulting path partially extends beyond (asshown by a hatched area) an arc drawn by the bucket nose point in thenose-fixed mode wherein the arm 2 is turned without moving the bucket 3with respect to the arm 2. Therefore, a target excavating surface isruined in the hatched area during automatic operation. Hence, it is verylikely that the operator's intention in this case is the fixed-angle tothe ground mode. Therefore, it is necessary to calculate these twopossibilities and determine the automatic operation mode according tothe magnitude of the calculated values.

Furthermore, an example of a prior art automatic operation in a powershovel is disclosed in Japanese Patent Laid-Open No. 2-221527publication. It comprises an actuator controlling means, which controlsactuators for an excavator; a working machine attitude detecting means,which detects the attitude angles of the boom, arm, and tip workingmachine of an excavating machine; a grade input means, which gives atarget excavating grade for a surface to be excavated by the tip workingmachine; a distal end inclination input means, which gives a targetinclination of the tip working machine with respect to a referenceplane; and an actuator operating amount computing means, which computesan operating amount for moving the tip working machine at a determinedspecific speed with the given inclination and the given excavating gradein response to a detected value received from the working machineattitude detecting means and command values received from the gradeinput means and the tip inclination input means, and supplies thecomputed value to the actuator controlling means.

However, in such a control apparatus, it is necessary to specify inputsignals including a grade input, a control inclination input, and anexcavating direction input for the excavating conditions of a slopesurface at the time the automatic operation is begun. Furthermore, thereis a problem in that the need for entering the input signals is easilyforgotten, and all inputs must be checked for correctness each timebefore the automatic operation is started.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method whereby theoperation mode can be automatically determined without the need fordetermining the angle to the ground β formed by the bottom surface ofthe bucket and a target grade, and without the need for correcting thespecific nose angle α even when the bucket is replaced by any optionalbucket having a special shape. The path control intended by an operatorcan be better performed automatically even when the suspension work isperformed by a hook attached to the rear of the bucket. The arithmeticprocessing can be performed easily, and the automatic determination ofthe operation mode can be performed more easily since the operation modeis automatically determined by an allowable angle to the ground and theattitude of the nose.

It is another object of the present invention to provide a methodwhereby operator fatigue from operation is reduced to a minimum, andoperation errors during excavating work are prevented by including thesignals for the excavating direction among the signals entered duringthe excavating work.

According to the first aspect of the present invention, a constructionequipment having a tip working machine, such as a bucket, wherein thedistal end of the tip working machine is subjected to linear pathcontrol, is provided with: a tip working machine attitude detectingmeans which detects the bucket attitude angle γ, which is the relativeattitude of the tip working machine with respect to the arm; anallowable angle computing section for calculating an angle δ, which isan allowable angle held with respect to the ground and which indicateshow long the tip working machine can hold the current angle to theground in the turning direction d of the tip working machine, the angleδ being calculated from the bucket attitude angle γ and the turningdirection d of the tip working machine; and an operation modedetermining section, which determines whether the operation mode is thenose-fixed mode, wherein the tip working machine holds the relativeattitude with respect to the arm, or the fixed-angle to the ground mode,wherein the angle to the ground is held constant; the determinationbeing made in accordance with the bucket attitude angle γ and theallowable angle held with respect to the ground δ when the automaticpath control is performed, the operation mode determining sectioncalculating a possibility U2 of the operation mode being the nose-fixedmode, according to how far the bucket attitude angle γ deviates from apredetermined angle and also calculating a possibility U1 of theoperation mode being the fixed-angle to the ground mode, according tothe magnitude of the calculated value of the allowable angle held withrespect to the ground, and automatically determining the operation modeduring the automatic path control by comparing the possibilities U1 andU2.

According to the second aspect of the present invention, a constructionequipment having a tip working machine, such as a bucket, wherein thedistal end of the tip working machine is subjected to linear pathcontrol, is provided with: a tip working machine attitude detectingmeans, which detects the bucket attitude angle γ which is a relativeattitude of the tip working machine with respect to the arm; anallowable angle computing section for calculating the allowable angleheld with respect to the ground δ, which indicates how long the tipworking machine can hold the current angle to the ground in the turningdirection d of the tip working machine, the angle δ being calculatedfrom the bucket attitude angle γ and the turning direction d of the tipworking machine; and an operation mode determining section, whichdetermines whether the operation mode is the nose-fixed mode, whereinthe tip working machine holds the relative attitude with respect to thearm, or the fixed-angle to the ground mode, wherein the angle to theground is held constant; the determination being made in accordance withthe allowable angle held with respect to the ground δ when the automaticpath control is performed, the operation mode determining sectioncalculating the possibility U1 of the operation mode being thefixed-angle to the ground mode, according to the magnitude of thecalculated value of the allowable angle held with respect to the ground,and automatically determining the operation mode during the automaticpath control in accordance with the magnitude of the possibility U1.

According to the third aspect of the present invention, a constructionequipment having a tip working machine, such as a bucket, wherein thedistal end of the tip working machine is subjected to linear pathcontrol, is provided with: a tip working machine attitude detectingmeans, which detects the bucket attitude angle γ, which is a relativeattitude of the tip working machine with respect to the arm; and anoperation mode determining section, which determines whether theoperation mode is the nose-fixed mode, wherein the tip working machineholds the relative attitude with respect to the arm, or the fixed-angleto the ground mode, wherein the angle to the ground is held constant;the determination being made in accordance with the bucket attitudeangle γ when the automatic path control is performed, the operation modedetermining section calculating the possibility U2 of the operation modebeing the nose-fixed mode, according to how far the bucket attitudeangle γ deviates from a predetermined angle, and automaticallydetermining the operation mode during the automatic path control inaccordance with the magnitude of the possibility U2.

In the individual aspects of the present invention described above, amode determining switch can be used to select whether the operation modeis determined automatically or is forcibly set to the nose-fixed mode orto the fixed-angle to the ground mode. In addition, whether the currentmode automatic determining value is for the nose-fixed mode or for thefixed-angle to the ground mode can be indicated by an indicator lampaccording to an output from the operation mode control section.Furthermore, a knob switch can be provided on the operating lever of theworking machine so that a determination value of the operation modedetermining section is inverted and outputted when the knob switch ispressed.

According to the fourth aspect of the present invention, since it isgenerally true that the excavation is in the pulling direction when thedistal end of the working machine is positioned at the back of a workingarea at the beginning of the excavation and is in the pushing directionwhen it is positioned at the front of the working area at the beginningof the excavation, the working area can be divided into two areas A andB by a boundary; a position detecting means provided on a workingmachine, which can be operated automatically, can determine to which ofthese two areas A and B a working condition, such as the angle andposition of the working machine, belongs and thus determine whether theexcavation is in the pushing direction or in the pulling direction inaccordance with the area determination. For determining the direction ofthe excavation, priority can be given to a command received from anexternal input switch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration explanatory view which shows the workingmachine of the hydraulic power shovel;

FIG. 2A is a configuration explanatory view which shows the nose-fixedmode;

FIG. 2B is a configuration explanatory view which shows the fixed-angleto the ground mode;

FIG. 3 is an explanatory view of the prior art;

FIG. 4A is a side view which shows the standard tooth bucket;

FIG. 4B is a side view which shows the slope surface bucket;

FIG. 5 is a diagram which shows the suspension work by the bucket;

FIG. 6A is a diagram which shows a state wherein the possibility ofbeing the nose-fixed mode is high;

FIG. 6B is a diagram which shows a state wherein the possibility ofbeing the bucket fixed-angle to the ground mode is high;

FIG. 7A is a block diagram which shows the first embodiment of thepresent invention;

FIG. 7B is a block diagram which shows the second embodiment of thepresent invention;

FIG. 7C is a block diagram which shows the third embodiment of thepresent invention;

FIG. 8A is a block diagram which shows an algorithm for calculating theallowable angle held with respect to the ground;

FIG. 8B is an explanatory view which shows the attitude of the bucket;

FIG. 9A is a block diagram which shows an algorithm of the firstembodiment of the present invention;

FIG. 9B is a block diagram which shows an algorithm of the secondembodiment of the present invention;

FIG. 9C is a block diagram which shows an algorithm of the thirdembodiment of the present invention;

FIG. 10A is an explanatory view which shows an application example ofthe present invention;

FIG. 10B is a block diagram which shows an algorithm of the applicationexample;

FIG. 11A is an explanatory view which shows a second application exampleof the present invention;

FIG. 11B is a block diagram which shows an algorithm of the secondapplication example;

FIG. 12 is a block diagram which shows the fourth embodiment of thepresent invention;

FIG. 13 is an explanatory view of the attitude of each component of theworking machine;

FIG. 14 is a diagram which shows a case wherein the working area of thearm is divided into two areas in accordance with the angle of the arm;

FIG. 15 is a two-dimensional view of a case wherein the workingdirection is determined in accordance with the angle of the arm;

FIG. 16 is a two-dimensional view of a case wherein the workingdirection is determined in accordance with the angle of the arm and theangle of the boom;

FIG. 17 is a two-dimensional view of a case wherein the workingdirection is determined by conversion to x-y coordinates;

FIG. 18A and FIG. 18B are two-dimensional views of a case wherein theworking direction is determined by conversion to x-y coordinates; and

FIG. 19 is a flowchart for determining the working direction by means ofthe external input switch.

BEST MODE FOR CARRYING OUT THE INVENTION

The first embodiment of the present invention will be described withreference to FIG. 7A and other figures. The parts which are the same asthose of the conventional example shown in FIG. 1 through FIG. 6B willbe indicated by the same reference numerals and the explanation thereofwill not be repeated.

In FIG. 7A, the bucket attitude detecting means 7 can determine thebucket attitude by various methods. In one method, the bucket attitudeangle γ, which is the angle of the bucket 3 around the rotary shaft withrespect to the arm 2, is detected by means of a potentiometer or arotary sensor such as an encoder. In a second method, the attitude of acylinder link section with respect to the arm 2 is detected by a rotarysensor, and a relative angle is determined from a geometric relationshipof the link section rather than directly detecting the angle around therotary shaft. In another method, the turning angle of the bucket 3 andthe length of the cylinder stroke are detected by a direct-actingpotentiometer or a linear encoder to determine the relative angle fromthe geometric relationship.

The computing section 8 determines the allowable angle held with respectto the ground by first determining the direction in which the bucket 3has to turn to hold the angle to the ground in view of the turningdirection d of the arm 2. For example, in general, the turning angle ofthe arm 2 is larger than that of the boom 1 during the nose pathcontrol; therefore, the bucket 3 turns in the opposite direction fromthe arm in order to maintain the angle to the ground constant.

The turning direction d of the arm 2 can be determined in accordancewith the following methods:

(a) If the operator instructs the excavating direction through aninstructing switch or the like, then whether a switch command signifiesthe arm excavating side (d>0) or the arm dump truck side (d<0) isdetermined from the state of the switch signal. This provides aunequivocal determination.

(b) In the case of an automatic operation based on the path control,wherein other shafts are automatically controlled in response to theleading operation of the arm shaft, and in the case of the master-slavetype automatic operation, wherein the direction is instructed in termsof a vector input, the operation signal of the arm shaft can bedetermined as plus or minus with respect to the turning direction d.

(c) The turning direction d can be automatically determined by whetherthe attitude of the arm 2 at the beginning of the automatic operation iscloser to the dump truck side or the excavating side. If the directiondetermining value is on the excavating side, then d>0; and if it is onthe dump truck side, then d<0.

The turning direction d of the arm 2, which has been obtained inaccordance with method (a), (b) or (c) described above, and the bucketattitude angle γ, which has been detected by the bucket attitudedetecting means, are supplied to the allowable angle computing section 8to determine the possible angle of rotation of the bucket 3 up to astroke end angle γ₀ on the turning direction side according to thealgorithm shown in FIG. 8A, and the determined value is taken as theallowable angle held with respect to the ground δ. FIG. 8B is theexplanatory view which shows the attitude γ of the bucket 3 with respectto the arm 2.

Therefore;

    δ=|γ.sub.0 -γ|         (2)

The bucket attitude angle γ and the allowable angle held with respect tothe ground δ thus obtained are supplied to the operation modedetermining section 9 to provide a possibility signal as a function ofthe allowable angle held with respect to the ground δ. For example, asshown in formula (3), the possibility signal U1 represents thepossibility of the fixed-angle to the ground mode.

    U1=K.sub.1 ·δ                               (3)

(K₁ is an appropriate coefficient.)

As shown in formula (4), the possibility signal U1 can be establishedstepwise in accordance with the magnitude of the allowable angle heldwith respect to the ground δ.

    U1=0.1 (when δ≧C1)                            (4)

    U1=0.5 (when C1>δ≧C2)

    U1=0.0 (when δ<C2)

(C1 and C2 are predetermined threshold values of the allowable angleheld with respect to the ground.)

On the other hand, the possibility signal U2, representing thepossibility of the nose-fixed mode, the maximum attitude on the dumptruck side (γ=γmin) is optimum because it is necessary to prevent therear of the bucket 3 from contacting the excavated slope surface.Further, in general, the nose is positioned as an extension of the armto secure a great length of excavation, thereby allowing a long reach(γ=0); therefore, the possibility U2 can be given as a function of thebucket attitude angle γ as shown in a formula (5):

    U2=K.sub.2 ·(γ.sub.S -γ).sup.2        (5)

(K₂ is an appropriate coefficient; γ_(S) is a predetermined referenceangle such as γ_(X) =0°)

Or as with the aforesaid formula (4), the possibility U2 can beestablished stepwise in accordance with the magnitude of the bucketattitude angle γ.

The magnitudes of the possibility signals U1 and U2 thus obtained arecompared in accordance with the algorithm shown in FIG. 9A: if U1>U2,then the fixed-angle to the ground mode is selected; and if U2>U1, thenthe nose-fixed mode is selected.

According to the first embodiment, a user does not have to correct thespecific nose angle α even when the tip working machine, such as thebucket 3, is replaced by any optional special bucket; and the operationmode is automatically determined in accordance with the allowable anglewith respect to the ground and the attitude of the nose even whensuspension work is carried out by the hook attached to the rear of thetip working machine, enabling improved automatic path control asintended by the operator.

There is another method whereby the mode can be determined merely by thepossibility U1 of the fixed-angle to the ground mode.

FIG. 7B and FIG. 9B show the second embodiment. First, in FIG. 7B, onlythe allowable angle held with respect to the ground δ, which has beencalculated by the allowable angle computing section 8 from the bucketattitude angle γ and the turning direction d of the bucket 3, issupplied to the operation mode determining section 9. In this case, thepossibility of the operation mode being the fixed-angle to the groundmode is calculated in accordance with the magnitude of δ, and theoperation mode during the path control is automatically determined inaccordance with the magnitude of this possibility. More specifically, asshown in FIG. 9B, the possibility U1 of the fixed-angle to the ground isdetermined from the allowable angle held with respect to the ground δ,and the magnitude of the determination result is compared with that of apredetermined threshold value U_(S). If U1>U_(S), then the fixed-angleto the ground mode is selected; while if U1<U_(S), then the nose-fixedmode is selected.

Alternatively, there is still another method whereby the mode isdetermined only from the possibility U2 of the nose-fixed mode.

FIG. 7C and FIG. 9C show the third embodiment. First, in FIG. 7C, thebucket attitude angle γ is supplied to the operation mode determiningsection 9 which calculates the possibility of the operation mode beingthe nose-fixed mode according to how far the bucket attitude angle γdeviates from the predetermined angle, and automatically determines theoperation mode during the path control in accordance with the magnitudeof the calculated possibility. More specifically, as shown in FIG. 9C,only the possibility U2 of the nose-fixed mode is compared with thepredetermined threshold value U_(S). If U2>U_(S), then the nose-fixedmode is selected; while if U2<U_(S), then the fixed-angle to the groundmode is selected.

In the second embodiment and the third embodiment, simplified automaticdetermination of the operation mode can be performed more easily bysimplifying the arithmetic processing.

FIG. 10A and FIG. 10B show an application example of the presentinvention. In FIG. 10A, a mode determining switch 10 allows theselection of one of the automatic setting mode, the fixed-angle to theground mode, and the nose-fixed mode. The indicator lamps 11 and 12,such as LEDs, show the selection result. FIG. 10B shows the algorithm inthis application example; the operation mode, which has been selectedthrough the mode determining switch, is forcibly outputted. Then themode can be checked by the lighting of the indicator lamps 11 and 12,thus making it possible to prevent the bucket 3 from taking a move whichis not intended by the operator. This is effective when the operatorwishes to operate only in one of the modes for safety. Furthermore,higher safety is secured since the operator can visually check the modeautomatic determination value before starting the operation.

FIG. 11A and FIG. 11B show another application example. An operatinglever 13 is provided with a knob switch 14 so that the modedetermination value is inverted according to the algorithm shown in FIG.11B if the knob switch 14 is pressed. If the mode is not what theoperator intended, then the operator can invert the mode, enabling himto continue the automatic operation without releasing the operatinglever.

The fourth embodiment of the present invention will now be describedwith reference to the drawings.

FIG. 12 is the block diagram which shows the fourth embodiment. For thesake of the description given below, the angles and positions of theindividual components of the power shovel are defined as shown in FIG.13. Specifically, the turning angle of a boom 11 is defined as θ₁, theturning angle of an arm 12 with respect to boom axis as θ₂, the turningangle of a bucket 13 with respect to the arm axis as θ₃, the inclinationof the bucket 13 with respect to the horizontal surface (referencesurface) as φ, the length of the boom 11 as L₁, the length of the arm 12as L₂, the length of the bucket 13 as L₃, the longitudinal position ofthe distal end of the bucket 13 as x, the vertical position of thedistal end of the bucket as y, and a target excavating grade as θ.

In such a configuration, a grade command θa from a grade input means 17,a bucket inclination command φa from a distal end inclination inputmeans 18, a detected value θ₁ a of the boom angle, a detected value θ₂ aof the arm angle, and a detection value θ₃ a of the bucket angle fromworking machine attitude detecting means 20a, 20b, and 20c,respectively, are supplied to an actuator operating amount computingmeans 19. This actuator operating amount computing means 19 calculates atarget inclination of the bucket 13, a target path of the nose, and anactual inclination and an actual path of the bucket 13, then itcalculates flow command values Vθ₁, Vθ₂, and Vθ₃ of a fluid to besupplied to the actuators for the boom 11, the arm 12, and the bucket 13in order to move along the target path at the obtained bucketinclination. Based on the computed values, flow control valves 21a, 21b,and 21c are controlled to drive cylinders 14, 15, and 16.

On the other hand, an excavating direction determining section 19adetermines the excavating direction of the bucket 13 in accordance withthe detected values θ₁ a, θ₂ a, and θ₃ a received from the workingmachine attitude detecting means 20a, 20b, and 20c, then outputs theresult to the aforesaid computing means 19. The excavating directiondetermining section 19a determines the excavating direction by using aninput value of an angle θ₂ of the arm, the angle θ₂ of the arm 12 and anangle θ₁ of the boom 11, or an x-y coordinate system of the distal endof the arm 12. Specifically:

(a) When the arm angle θ₂ is used for the determination:

As shown in FIG. 14, a working area of the arm 12 is divided into twoareas based on a certain arm angle θ₂₀. This reference angle θ₂₀ is setin the excavating direction determining section 19a in advance, and thispreset reference angle is compared with the detected value θ₂ of the armreceived from the working machine attitude detecting section 20b for thearm to determine the excavating direction.

    θ.sub.20 =ε.sub.0                            (6)

ε₀ : Set value

If θ₂ ≦θ₂₀, then the working area will be a farther area A and theexcavation will be in the pulling direction. If θ₂ >θ₂₀, then theworking area will be a closer area B and the excavation will be in thepushing direction. For example, if θ₂₀ =100° and a control start pointis θ₂ =135° then θ₂ >θ₂₀, which means the area B; therefore, theexcavation will be in the pushing direction. This is showntwo-dimensionally in FIG. 15.

(b) When the arm angle and the boom angle are used for thedetermination:

As shown in FIG. 16, the following boundary which divides the workingarea into two areas is A and B set in advance:

    f (θ.sub.10, θ.sub.20)=0                       (7)

The boom angle θ₁ and the arm angle θ₂ are substituted in the formula(7) and whether the working area belongs to the area A or to the area Bdepends on whether the left side member is positive or negative. Theexcavation will be in the pulling direction in the case of the area A,while the excavation will be in the pushing direction in the case of thearea B.

For example, the boundary expressed by the following formula is set:

    f (θ.sub.10, θ.sub.20)=θ.sub.10 +θ.sub.20 -160=0(8)

And if the control start point is (θ₁, θ₂)=(100, 55), then

    f (θ.sub.1, θ.sub.2)=100+55-160<0              (9)

and the working area is determined as the farther area A, the excavationbeing in the pulling direction.

(c) When conversion into the x-y coordinate system is used for thedetermination (part 1):

From FIG. 13, the position (x, y) of the distal end of the arm isdetermined by

    x=L.sub.1 sin θ.sub.1 +L.sub.2 sin (θ.sub.1 +θ.sub.2),

    y=L.sub.1 cos θ.sub.1 +L.sub.2 cos (θ.sub.1 +θ.sub.2)(10)

And the boundary for dividing the working area into two areas as shownin FIG. 17, which is determined by the formula given below is set inadvance:

    f (X.sub.0, Y.sub.0)=0                                     (11)

And x, y are substituted in the formula (11) and the area to which theworking area belongs is determined by whether the left side member ispositive or negative. The excavation will be in the pulling direction inthe case of the area A, while the excavation will be in the pushingdirection in the case of the area B.

For instance, f (X₀, Y₀)=X₀ ² +Y₀ ² -5000² =0 is set and if the controlstart point (x, y) is (x, y)=(7000, 200) which is determined by theformula (10), then f (x, y)=(7000² +2002-5000²)>0, and the working areais determined as being the area A, the excavation being in the pullingdirection.

(d) When the conversion to the x-y coordinate system is used for thedetermination (part 2):

From FIG. 18A, with a point 0 of a boom top pin taken as the center ofthe coordinate, the position of the bucket nose is determined by

    x=L.sub.2 sin (θ.sub.1 +θ.sub.2 -θ)+L.sub.3 sin (θ.sub.1 +θ.sub.2 +θ.sub.3 -θ)    (12)

X₀ =0 is defined in advance as shown in FIG. 18B, and this is comparedwith the x above: if x>x₀, then the excavation will be in the pullingdirection; and if x<x₀, then it is in the pushing direction.

The boundary for dividing the working area into two areas, which isexpressed by the formulas given above, can be fixed or it can varyaccording to the excavating grade or the angle of the working machine.For example, it can be preset as follows: if the excavating grade θ is≦30°, then θ₂₀ =100°; and if the excavating grade θ is >30°, then θ₂₀=70°.

In addition, if the operator wishes to optionally decide the excavatingdirection, a changeover switch 22 is provided as shown in FIG. 12 andthe operator sets for the pulling side or the pushing side by givingpriority to the signal of the external input switch. In this case, theprocessing flow will be as shown in FIG. 19.

According to the fourth embodiment, the need of including the excavatingdirection among the input signals issued during excavating work iseliminated. This reduces operator fatigue from operation, preventing anoperation error.

INDUSTRIAL APPLICABILITY

The present invention is useful as an automatic operation mode selectingmethod for a working machine, which method eliminates the need ofcorrecting the angle of a bucket nose by a user even when the bucketprovided on a construction machine, such as a hydraulic power shovel, isreplaced by any optional special bucket, and enables path control asintended by an operator.

We claim:
 1. Apparatus for selecting an automatic operation mode of aworking machine in a construction equipment, wherein a distal end of atip working machine is subjected to automatic linear path control andthe tip working machine is associated with an arm, said apparatuscomprising:a tip working machine attitude detecting means, which detectsa tip working machine attitude angle which is a relative attitude of thetip working machine with respect to the arm; an allowable anglecomputing section for calculating an allowable angle held with respectto the ground, which indicates how long the tip working machine can holda current angle to the ground in a turning direction of the tip workingmachine, the allowable angle being calculated from the tip workingmachine attitude angle and the turning direction of the tip workingmachine; and an operation mode determining section, which determineswhether an operation mode is a nose-fixed mode, wherein the tip workingmachine holds the relative attitude with respect to the arm, or afixed-angle to the ground mode, wherein the angle to the ground is heldconstant; wherein said operation mode determining section makes thedetermination in accordance with the tip working machine attitude angleand the allowable angle held with respect to the ground when automaticlinear path control is performed, with the determination being made bythe operation mode determining section calculating, according to how farsaid tip working machine attitude angle deviates from a predeterminedangle, a first possibility (U2) of the operation mode being thenose-fixed mode; by the operation mode determining section calculating,according to the magnitude of the calculated value of the allowableangle held with respect to the ground, a second possibility (U1) of theoperation mode being the fixed-angle to the ground mode; and by theoperation mode determining section automatically determining theoperation mode during the automatic path control by comparing the thuscalculated first and second possibilities (U2 and U1).
 2. Apparatus inaccordance with claim 1, further comprising a mode determining switchfor manually selecting whether said operation mode is to beautomatically determined, or the nose-fixed mode or the fixed-angle tothe ground mode is to be forcibly set.
 3. Apparatus in accordance withclaim 1, further comprising indicator lamps and means for applying anoutput from the operation mode determining section to the indicatorlamps to show whether an automatic determination value of said operationmode indicates the nose-fixed mode or the fixed-angle to the groundmode.
 4. Apparatus in accordance with claim 1, further comprising anoperating lever of said working machine, a knob switch provided on saidoperating lever, and means for inverting a determination value of theoperation mode determining section and outputting the thus inverteddetermination value when the knob switch is actuated.
 5. Apparatus forselecting automatic operation mode of a tip working machine inconstruction equipment, wherein a distal end of the tip working machineis subjected to automatic linear path control and the tip workingmachine is associated with an arm, said apparatus comprising:a tipworking machine attitude detecting means, which detects the tip workingmachine attitude angle, which is a relative attitude of the tip workingmachine with respect to the arm; an allowable angle computing sectionfor calculating an allowable angle held with respect to the ground,which indicates how long the tip working machine can hold a currentangle to the ground in a turning direction of the tip working machine,the allowable angle being calculated in accordance with the tip workingmachine attitude angle and the turning direction of the tip workingmachine; and an operation mode determining section, which determineswhether the operation mode is a nose-fixed mode, wherein the tip workingmachine holds the relative attitude with respect to the arm, or afixed-angle to the ground mode, wherein the angle to the ground is heldconstant; wherein said operation mode determining section makes thedetermination in accordance with said allowable angle held with respectto the ground when the automatic linear path control is performed, withthe determination being made by the operation mode determining sectioncalculating, according to the magnitude of the calculated value of theallowable angle held with respect to the ground, a possibility (U1) ofthe operation mode being the fixed-angle to the ground mode, and by theoperation mode determining section automatically determining theoperation mode during the automatic linear path control in accordancewith the magnitude of the thus calculated possibility (U1).
 6. Apparatusin accordance with claim 5, further comprising a mode determining switchfor manually selecting whether said operation mode is to beautomatically determined, or the nose-fixed mode or the fixed-angle tothe ground mode is to be forcibly set.
 7. Apparatus in accordance withclaim 5, further comprising indicator lamps and means for applying anoutput from the operation mode determining section to the indicatorlamps to show whether an automatic determination value of said operationmode indicates the nose-fixed mode or the fixed-angle to the groundmode.
 8. Apparatus in accordance with claim 5, further comprising anoperating lever of said working machine, a knob switch provided on saidoperating lever, and means for inverting a determination value of theoperation mode determining section and outputting the thus inverteddetermination value when the knob switch is actuated.
 9. Apparatus forselecting an automatic operation mode of a working machine in aconstruction equipment, wherein a distal end of a tip working machine issubjected to automatic linear path control and the tip working machineis associated with an arm, said apparatus comprising:a tip workingmachine attitude detecting means, which detects a tip working machineattitude angle which is a relative attitude of the tip working machinewith respect to the arm; and an operation mode determining section,which determines whether an operation mode is a nose-fixed mode, whereinthe tip working machine holds the relative attitude with respect to thearm, or a fixed-angle to the ground mode, wherein the angle to theground is held constant; wherein said operation mode determining sectionmakes the determination in accordance with the tip working machineattitude angle when automatic linear path control is performed, with thedetermination being made by the operation mode determining sectioncalculating, according to how far said tip working machine attitudeangle deviates from a predetermined angle, a possibility (U2) of theoperation mode being the nose-fixed mode; and by the operation modedetermining section automatically determining the operation mode duringthe automatic linear path control in accordance with the magnitude ofthe thus calculated possibility (U2).
 10. Apparatus in accordance withclaim 9, further comprising a mode determining switch for manuallyselecting whether said operation mode is to be automatically determined,or the nose-fixed mode or the fixed-angle to the ground mode is to beforcibly set.
 11. Apparatus in accordance with claim 9, furthercomprising indicator lamps and means for applying an output from theoperation mode determining section to the indicator lamps to showwhether an automatic determination value of said operation modeindicates the nose-fixed mode or the fixed-angle to the ground mode. 12.Apparatus in accordance with claim 9, further comprising an operatinglever of said working machine, a knob switch provided on said operatinglever, and means for inverting a determination value of the operationmode determining section and outputting the thus inverted determinationvalue when the knob switch is actuated.
 13. Apparatus for selectingautomatic operation mode of a tip working machine of an excavatingconstruction equipment having an arm associated with said tip workingmachine, a boom associated with the arm, a tip working machine actuatorassociated with the tip working machine, an arm actuator associated withthe arm, and a boom actuator associated with the boom, said apparatuscomprising:a detector for providing an attitude angle signalrepresentative of a turning angle of the tip working machine withrespect to the arm, a detector for providing an arm angle signalrepresentative of a turning angle of the arm with respect to the boom, adetector for providing a boom angle signal representative of a turningangle of the boom, an excavating direction determining unit forproviding a direction signal representative of an excavating directionof the tip working machine, a grade input device for providing a gradesignal representative of the grade of a surface to be excavated; aninclination input devices for providing a inclination signalrepresentative of a target inclination of the tip working machine withrespect to a reference plane, and an actuator operating amount computerfor receiving the attitude angle signal, the arm angle signal, the boomangle signal, the direction signal, the grade signal, and theinclination signal, and providing responsive thereto actuator controlsignals for controlling the tip working machine actuator, the armactuator, and the boom actuator so that a distal end of the tip workingmachine follows a target path.
 14. Apparatus in accordance with claim13, wherein said excavating direction determining unit receives theattitude angle signal, the arm angle signal, and the boom angle signal,and provides responsive thereto the direction signal representative ofan excavating direction of the tip working machine.
 15. Apparatus inaccordance with claim 13, wherein said excavating direction determiningunit is provided with a preset reference signal representing a certainarm angle, and wherein said excavating direction determining unitreceives the arm angle signal and compares the arm angle signal with thepreset reference signal, and provides the direction signal in responseto the comparison.
 16. Apparatus in accordance with claim 15, whereinthe tip working machine is excavating in a pushing direction when thearm angle signal is greater than the preset reference signal, and thetip working machine is excavating in a pulling direction when the armangle signal is smaller than the preset reference signal.
 17. Apparatusin accordance with claim 13, wherein said excavating directiondetermining unit receives the arm angle signal and the boom anglesignal, and provides responsive thereto the direction signalrepresentative of an excavating direction of the tip working machine.18. Apparatus in accordance with claim 13, wherein said excavatingdirection determining unit provides the direction signal in response tox-y coordinate system position of a distal end of the arm.
 19. Apparatusin accordance with claim 13, wherein said excavating directiondetermining unit provides the direction signal in response to x-ycoordinate system position of a distal end of the tip working machine.20. Apparatus in accordance with claim 13, further comprising anexternal input switch, wherein said excavating direction determiningunit gives priority to the external input switch during the automaticdetermination of the excavating direction of the tip working machine.